HEALTH: Is Milk as healthful as we think?

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Many people include milk in their diet, but few meet the daily recommended quantities. Experts now urge us to rethink these recommendations and explain why milk may not be as healthful as we think.

Dairy milk’s image has taken a bit of a beating, with the likes of oat, almond, and soy milk being hailed as environmentally friendly alternatives.

But for many people of all ages, cow’s milk remains a firm favorite —sloshed over cereal, as a frothy companion to coffee, or enjoyed as a bedtime drink.

The United States 2015-2020 Dietary Guidelines recommend that individuals aged 9 years and over consume 3 cup-equivalents of fat-free and low-fat (1%) dairy products. According to the guideline, put together by the U.S. Department of Health and Human Services and the U.S. Department of Agriculture, this includes milk, yogurt, cheese, and fortified soy milk.

Yet the average amount of dairy that U.S. adults consume is around 1.6 cups each day, far short of the recommended levels.

Does that mean we should all look to increase our dairy consumption?

Experts writing in the New England Journal of Medicine do not think so. Instead, they call into question the quality of the evidence underpinning these recommendations and suggest alternative sources to provide us with the nutrients necessary for our health.

Strength of evidence is limited

The debate about milk is, in fact, not a new one.

Back in 2014, Connie M Weaver, emeritus professor and formerly the Head of the Department of Nutrition Science at Purdue University in West Lafayette, IN, wrote an article in The American Journal of Clinical Nutrition highlighting the lack of good quality evidence in support of dairy guidelines.

In her article, which was, in part, funded by Danone Institute International, Weaver alludes to the historical reasons behind milk’s importance to our diet.

“Dairy foods play a central role in most dietary guidance recommendations. They provide a package of essential nutrients and bioactive constituents for health that are difficult to obtain in diets with no or limited use of dairy products,” Weaver writes.

Since the agricultural revolution, when energy sources shifted from plant foods relatively high in calcium in the diets of hunter-gatherers to cereal crops with low calcium content, the major source of dietary calcium has been milk,” she continues.

Milk has featured in every iteration of the U.S. Dietary Guidelines since its first publication in 1917. Every 5 years, the Dietary Guidelines for Americans Advisory Committee updates the guide, reviewing the available evidence.

Weaver references research that highlights how following a dairy-free diet in the context of a U.S.-style Western diet left adolescents aged 9 –18 years struggling to achieve the recommended intake of calcium.

For the purpose of meeting daily nutrient intake, milk and cheese contribute “46.3% of calcium, 11.6% of potassium, and 7.9% of magnesium in the American diet.”

Yet, when it comes to health overall, Weaver writes, “the strength of the evidence for dairy consumption and health is limited by the lack of appropriately powered randomized controlled trials.”

Human health and the environment

Fast forward to 2020, and a new review article in the New England Journal of Medicine picks up the argument.

Dr. Walter C. Willett and Dr. David S. Ludwig, who both hold positions at Harvard T.H. Chan School of Public Health and Harvard Medical School in Boston, MA, discuss the merits of milk. They also pose questions about the possible risk that consuming it may carry.

Both Dr. Willett, a professor of epidemiology and nutrition, and Dr. Ludwig, an endocrinologist, declare no relevant conflicts of interest or industry sponsorship for their article.

Medical News Today asked Dr. Willett why he is interested in studying the relationship between milk consumption and health.

“This is an important topic because milk is one of few foods that are specifically part of dietary guidelines in the U.S. and many other countries, and the recommended amount in the U.S. (3 glasses per day or equivalent amounts of cheese or other dairy products) would make up a large part of an overall diet,” he explained.

“However, studies over the last several decades have not clearly supported the need for such high intakes for prevention of fractures, which has been the main justification, and some concerns about harm have been raised,” he continued. “We thus thought an overview of evidence on risks and benefits would be useful.”

But health is not Dr. Willett’s only concern.

“Also, milk has a heavy environmental footprint, especially greenhouse gas production, and if everyone consumed 3 glasses per day, this would make avoiding extreme globally warming very difficult,” he elaborated. “This should be at least be considered when making decisions about production and consumption of milk.”

Studies have serious’ implications

In their article, the professors highlight the contributions that milk may make to the multitude of aspects of our health.

Bone health is probably the most familiar to many people.

Milk is a ready source of calcium, a mineral central to developing and maintaining good bone function. Yet, the studies that set the daily recommendations for how much milk and by extension calcium, we should consume, were very small.

“The basis for the U.S. recommendations for milk consumption derives from studies assessing the balance of calcium intake and excretion in just 155 adults in whom the estimated calcium intake needed to maintain balance was 741 mg per day,” the professors write in their article.

“Beyond small size, these balance studies have other serious limitations, including short duration (2 to 3 weeks) and high habitual calcium intakes,” they continue.

The evidence does not support milk consumption to reduce the risk of hip fractures, they further explain.

On the contrary, they point out that countries with high milk and calcium intake also have the highest hip fracture rates.

They reference a 2014 study in JAMA Pediatrics by Dr. Willett that examined the risk of hip fracture in men in relation to how much milk they drank during their adolescent years.

The results showed that higher milk consumption leads to an increased risk of hip fractures later in life.

How quickly and how tall we grow are two other examples. Research has established a link between these and milk consumption. Yet, the professors urge caution when drawing conclusions at this point.

“The health consequences of accelerated growth and greater adult height are complex,” they write. “Tall stature is associated with lower risks of cardiovascular disease but with higher risks of many cancers, hip fractures, and pulmonary emboli.”

Weight, heart health, and cancer

Dr. Willett and Dr. Ludwig then turned their attention to a host of other aspects of our health that milk consumption may or may not affect.

Several studies have investigated whether milk consumption is beneficial for weight management in adults and children. The professors argue that these showed no “clear effects.”

Moreover, they point out that “contrary to U.S. Department of Agriculture (USDA) advice to choose reduced-fat dairy, low-fat milk does not appear to have advantages over whole milk for weight control — and in children, available evidence suggests greater long-term weight gain with reduced-fat milk than with full-fat milk.”

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